1. Field of the Invention
This invention relates to rigging of aircraft Wing flaps, more particularly it relates to the rigging of trailing edge flaps for aircraft wings.
2. Discussion of Prior Art
"Rigging" or accurate positional setting of aircraft trailing edge flaps to a "zero" or in-flight cruise position requires the movable trailing edge flap to be accurately rigged with respect to the vertical positioning of its upper surface and the fore and art positioning of its trailing edge, both being in relation to a fixed wing structure of the aircraft. Such fixed wing structure is usually a central main torsion box of the wing comprising front and rear spanwise extending spars and upper and lower wing skins connecting the spars. For commercial aircraft the in-flight cruise configuration of a wing is critical as the fuel efficiency of the aircraft depends largely upon the aerodynamic efficiency of the wing when in cruise.
Trailing edge flaps may be movable between several positions to provide varying degrees of lift enhancement to the wing for operations such as take-off and landing and low speed approach. For these operations the trailing edge flap is movable between a cruise position in which it sits immediately behind the wing box with its upper and lower surfaces forming continuations of extentions from the wing box upper and lower skin surfaces and one or more deployed positions in which the flap is translated rearwardly and downwardly from the cruise position at the same time as being rotated. This combined translatory and rotational movement is normally achieved, at least on civil aircraft, by mounting the flap on two or more flap track beams depending downwardly and rearwardly from the wing box and affixed thereto. The flap is normally mounted for rolling or sliding movement along a track of the flap track beam. Where rolling movement is provided the flap is normally pivotally mounted on a wheeled carriage which rolls on the said track of the beam. Rearward deployment of the flap from the cruise position is then achieved by some form of actuating means which, usually in a combined movement, translates the carriage rearwardly along the track of the beam at the same time as pivoting the flap about its pivot on the carriage. Alternatively, or in addition, a curved track on the beam may provide the rotational movement of the flap during rearward translation.
Although the relative positioning of the upper surface of the flap and the upper skin of the wing box in a vertical plane is critical, to date methods and tools used for flap rigging have been subject to considerable variation depending upon the air temperature and time of day at which flap rigging has taken place. This is because known flap rigging tools are located on the upper skin of the wing box and such location has allowed changes in camber of the wing box with temperature variation greatly to affect the relative positions of parts of the tool from which flap setting measurements were taken and the flap trailing edge. In addition to this, these known tools are of considerable length and thereby subject to distortion and damage.